DISCOVERIES.

Drinking in tooth decay

A new study suggests soft drinks and powdered beverages cause more cavities in kids than fruit juice, but even orange juice can spell trouble if children overdo it.

When sugar reaches the teeth, it interacts with bacteria. "You produce acid as a byproduct," explained study co-author Teresa A. Marshall, a clinical assistant professor of preventive and community dentistry at the University of Iowa. The acid erodes the enamel of teeth.

Children with more cavities reported drinking more soft drinks and powdered beverages. Kids who drank a lot of fruit juice had more cavities, too, "but it was really a much lower effect than we saw with the other two beverages," Marshall said. "This doesn't mean that excessive drinking of juice is perfectly safe. But it isn't as bad as the others."

The researchers didn't notice any unusual cavity problems among children who drank a lot of juice drinks that were not 100 percent juice. It's not clear why fruit juices are better for the teeth than the other beverages, considering that they all come loaded with sugar, Marshall said.

Marshall and her colleagues report their findings in the September issue of Pediatrics.

All mercury isn't equal

The mercury in swordfish, tuna and other underwater species isn't as toxic as the mercury scientists use to gauge the dangers of eating seafood, a new study says.

Mercury is a toxin that in high doses can destroy nerve cells and trigger heart attacks, but the new study found the form of mercury most prevalent in certain food fish appears to be far less harmful than methylmercury chloride, the molecule on which cautions about fish consumption are based.

Mercury researcher Gary J. Myers said the findings point up the importance of studying mercury as it appears in the diet. "We hope that other people around the world will study populations that actually consume fish as their source of mercury," Myers said.

Studying the inhabitants of the Seychelles Islands in Africa, Myers' group has found no solid evidence that babies born to women in the Seychelles, where fish is a staple, suffer neurological deficits later in life.

Some ocean fish are higher in mercury than others.

The U.S. Food and Drug Administration recommends pregnant women avoid eating swordfish, shark, tilefish and king mackerel altogether. Other fish and shellfish should be limited to no more than 12 ounces per week, or between two and four servings. Most people in this country eat only one fish dish a week.